Local wall shape, principal fiber directions and curvatures will be mapped in the left and right ventricles of 24 autopsy hearts. The entire heart will be encapsulated in 10 percent gelatin, hardened by refrigeration, then sectioned in a miter box equatorially through the LV/RV equator and longitudinally on the prime meridianal plane bisecting LV and RV. Orthogonally oriented fiducials will be burned by hot needles into each of 2 LV free wall, 2 septal, and 3 RV free wall sites prior to excision of through-wall blocks containing them. X-Y coordinates of local wall shape and fiducial dimensions will be recorded by X-Y digitizer. Using an innovative method of sectioning of a prestained paraffin block, we will obtain through-wall sections at a regular sequence of alpha1 angles (the principal fiber component in a plane parallel to the local epicardium). On each section, stained with a trichrome stain, we will record by light microscopy and X-Y digitizer the location of the in-plane fibers and their angle beta (which measures the extent to which the fiber direction departs from the direction of the epicardial tangent). Using standard graphics software and Calcomp pen-plotting equipment we will generate 3-dimensional perspective plots of principal fiber pathways in the LV and RV walls that will facilitate comparisons of normal to abnormal ventricles. These pathways are known to be important to a stress analysis of the wall and also to an understanding of the bioelectric course of depolarization.